Istanbul: Turkish president Recep Tayyip Erdogan on Sunday welcomed Qatar's dismissal of a sweeping list of demands from Saudi Arabia and its allies in an escalating crisis and said the ultimatum was "against international law."

"We welcome (Qatar's position) because we consider the 13-point list against international law," Erdogan was quoted as saying by the state-run Anadolu news agency.

Erdogan, who spoke to reporters after morning prayers at an Istanbul mosque, said the demands on its embattled regional ally Qatar had gone "too far."

File image of Turkey president Recep Tayyip Erdogan. AP

"What we are talking about here is an attack on the sovereign rights of a state," he said.

"There cannot be such an attack on countries' sovereignty rights in international law."

Qatar on Saturday denounced the ultimatum as unreasonable and an impingement on the emirate's sovereignty.

Saudi Arabia, Bahrain, the United Arab Emirates and Egypt want Qatar to meet the 13-point ultimatum in return for an end to a nearly three-week-old diplomatic and trade "blockade" of the emirate.

The four Arab governments delivered the demands to Qatar through mediator Kuwait on Thursday, more than two weeks after severing all ties with the emirate and imposing an embargo.

The document which has not been published but has been widely leaked includes the closure of Al-Jazeera television, a long-standing source of conflict between Doha and neighbouring countries which accuse it of fomenting regional strife.

Notably, Doha has also been asked to shut a Turkish military base in the emirate.

'Disrespect'

The Turkish parliament passed a bill in June allowing Ankara to send up to several thousand troops to the Turkish base in Qatar.

Almost two dozen Turkish troops also arrived in Qatar as Ankara boosts military support for Doha.

Erdogan on Sunday said demanding the withdrawal of Turkish troops from Qatar was a "disrespect to Turkey."

The Turkish president also repeated an offer to Saudi Arabia to build a military base in the Muslim kingdom, similar to that built in neighbouring Qatar.

That offer was rejected by Riyadh which said a Turkish military base would not be welcome and "not needed."

"If Saudi Arabia wants us to build a base there, we can take a step in that direction," Erdogan said, adding that Riyadh had not responded to the latest proposal.

He also stood by the defence agreement with Qatar.

"Will we take permission from others when we cooperate on defence with a country? No offence, but Turkey is not an ordinary country, it is not an ordinary state," he said.

Since the crisis erupted between Doha and its Gulf neighbours, Erdogan has vowed to back Qatar and rejected the accusations that it supports terrorism.

But Ankara has stopped short of directly criticising Saudi Arabia's actions, merely calling on Riyadh to take a lead role in solving the crisis.